Caramelized teriyaki onions and creamy cheese sauce top a fresh custom ground patty for a cheddar melt burger that you'll remember for months to come.
Add onions to the melted butter
In a cast iron skillet or stainless steel pan over medium heat, melt the butter. Add the teriyaki sauce and stir in the sliced onions until they are completed coated.
Caramelize the onions
Stirring occasionally, cook for 45 minutes until the onions are completely broken down and they become golden and very fragrant. Scrape up the fond that continually forms as the onions caramelize with a wooden spoon or sturdy spatula. (Fond is a dark, sticky glaze that might make you think you're burning pan — but you're not). Reduce the heat if you notice the onions are developing burnt edges.
Deglaze the onions
The longer the onions cook, the deeper and richer their flavor will be. When the onions have reached your desired level of caramelization, deglaze the pan with the water. Incorporate the last bit of fond and salt the onions. The onions can be refrigerated for about 1 week.
Mix the cheese
In a small mixing bowl, toss together the shredded cheddar cheese with the corn starch.
Cook the cheese sauce
In a medium saucepan over low heat, add the cheese mixture and dry mustard to the evaporated milk. Whisking constantly, cook the cheese sauce for 5-7 minutes or until the shredded cheese is completely melted and the sauce starts to become bubbly. Add additional evaporated milk if you would like a thinner sauce.
Grind meat and make the patties
Using a the food grinder attachment for a stand mixer (configured for coarse grind), grind the chuck and sirloin together into a medium bowl. Form the meat mixture into 4 ounce patties. Gently press your thumb into the center of each patty to make a small indentation to prevent swelling.
Cook the burgers
Heat a cast iron skillet or griddle over medium-high heat. Add the salt to the burgers immediately before cooking. Being careful not to overcrowd the skillet, place the burgers in the skillet (indentation facing up) and cook them for about 10-12 minutes until the burger has developed a nice sear on the bottom side (after about 5 minutes or so). Flip the burger and cook for another 5-7 minutes until a safe temperature of 160 degrees F has been reached. Resist the temptation to press down on the burgers while cooking as this will dry out your burger.
Assemble the burgers
Butter the cut side of each bun half and cook for 2-3 minutes on the skillet (still set to medium-high heat) until the buns become golden brown and slightly crispy around the edges. Top the bun heels with the burgers, teriyaki onions and cheese sauce. Cover each burger with the bun crown and serve.